Rinnai Rinnai RE180iN RE Series Non-Condensing Tankless Water Heater MIN FLOW Error Fix: Minimum Flow Rate Not Met

Error code MIN FLOW on the Rinnai Rinnai RE180iN RE Series Non-Condensing Tankless Water Heater means: Minimum Flow Rate Not Met. The open hot water fixture is not providing enough water flow to activate or keep the tankless water heater running. All tankless water heaters have a minimum activation flow rate — typically 0.4 to 0.6 GPM for Rinnai residential models. When the water flow drops below this threshold, the unit shuts off the burner because it cannot safely modulate to such a low heat output. This commonly occurs with: (1) Low-flow bathroom sink faucets with restrictive aerators (0.5 GPM or less). (2) Trickle-flow situations where a fixture valve is barely opened. (3) Reduced flow from a whole-house filter that is overdue for replacement. (4) Municipal water pressure drops during peak usage. (5) A recirculation pump operating at a flow rate below the unit's activation threshold. This is a normal operational characteristic, not a malfunction. To address: remove or replace restrictive aerators with higher-flow versions. Ensure household water pressure is adequate (40-80 PSI recommended). Clean or replace whole-house water filters. On some newer Rinnai models, the minimum activation flow rate has been reduced to as low as 0.26 GPM.

The most successful fix is "Diagnose and Repair Low Flow Issues with Recirculation Pump or Plumbing" (medium difficulty, ~45 minutes). Estimated DIY cost: $10-$30. HomeMD has 2 community-ranked fixes for this error.

This error is rated info severity. It is generally not urgent and can often be resolved with a simple DIY fix.

Yes — the top-ranked community fix ("Diagnose and Repair Low Flow Issues with Recirculation Pump or Plumbing") is rated medium difficulty and takes about 45 minutes. Tools needed: Flow meter, Adjustable wrench, Pipe wrench, Multimeter.

DIY cost: $10-$30. Professional repair typically costs $120-$200. Many homeowners save money by trying the top-ranked community fix first.

The Rinnai Rinnai RE180iN RE Series Non-Condensing Tankless Water Heater has 8 other known error codes, including: 02 (Ignition Failure), 03 (Bath Fill Function Abnormality), 05 (Blocked Exhaust / Air Supply), 10 (Blocked Exhaust — Air Pressure Switch), 11 (No Ignition), and 3 more.

Error code MIN FLOW also appears on 8 other Rinnai models: Rinnai RL75iN RL Series Tankless Water Heater, Rinnai RL94iN RL Series Tankless Water Heater, Rinnai RSC160iN Condensing Combi Boiler, Rinnai RU130iN Sensei Super High Efficiency Plus Tankless Water Heater, Rinnai RU199iN Sensei Super High Efficiency Plus Tankless Water Heater, Rinnai RUR199iN Sensei Recirculating Tankless Water Heater, and 2 more. The fix may vary by model, so check each model's specific page for tailored repair steps.